Electric conductor.



No. VHA-5%.

v. LQWENDAHL. ELEG-"rma GUNDUGTGR,

APPLIATIO FILED FEB. 7.` 1903. 50 GIIEL.A

Carre/r. yr@ es PATBNTED DEC. 22, 1903.v

NiTnD STATES VICTOR LWENDAHL, OF STOCKHOLM, SWEDEN. i

ELECTRIC coNouc-ros.

SPECIFICATION forming part Uf Letters Patent N 0. 747,454, dated Decemineln 22, 1903.

Application filed February?, 1903. Serial No. 142,404. (No model.)

To all whom it may con/cern:

Be it known that I/Vioros LWENDAHL, manager, of Regeringsgatan 30, Stockholm, in the Kingdom of Sweden, do hereby declare the nature of my invention for Improvements in the Manufacture of Electric Conductors, and in what manner the same'is to be performed, to be particularly described and ascertained in and by the following statement.

The present invention relates to improvements in the`manufacture of electric conductors which are suitable, among other applications, for use as brushes for dyn-amos and electric motors and combine the good qualities of both carbon and met-al brushes and are at the same time free from the disadvantages connected therewith.

In the accompanying drawing is'shown on an exaggerated scale a conductor partly in section.

Carbon brushes are well-known to be poorer conductors and to oier greater resistance to electricity than metallic brushes; but the sparking and the wear of the coinmutator when carbon brushes are used are so small in comparison to thatiwhich takes place with metallic brushes that carbon brushes are generally preferred when the construction of the machine permits. Carbon brushes, however, sufer from one serious disadvantage, more especiallywhen theload is great-viz., that of depositing a layer of carbon on the commutator and at the same time throwing oi sparks, which layer of carbon interferes with the working of the machine and must be removed daily. The formation of sparks is no doubt due to the fact that the carbon brushes consist of a mechanical mixture of carbon powder of a comparatively high conductivity and a coked adhesive of less conductivity, non-conductive passages and pores being left between the particles,which causes the current to pass chiefly in the form of sparks between the commutatorand the portions of the brushes which conduct the best.

According to the present invention the above-mentioned disadvantages are lessened or overcome -by manufacturing' the electric conductors of grains of carbon coated by gaivanic action-for instance, with a layer ofi metal (for instance, copper)-and subtel quently compressed (preferably in a vacuum) without the use of any adhesive into a solid body of the desired shape and hardness. ln this manner 'a perfectly homogeneous body is obtained which is free from passages and pores and forms a coherent metallic conductor with grains of carbon embedded therein and which not only has a higher conductivity and offers less resistance to the passage of the current than the above-mentioned condoctors composed of carbon and a coked adhesive, but throws oli no sparks and deposits no carbon on the commutator during use.

The high resistance to wear characteristic of the electric conductors made according to the present invention is due to the metallic envelops surrounding 'the carbon grains, when compressed being wrinkled so 'to mesh into each other and become connected tcgether mechanically in the most intimate manner.

' The accompanying` drawing shows the grains of carbon and the metallic envelop designated by words applied thereto.

As an alternative the metal-coated grains of carbon may evidently be tinned before compression, in which case the strength of the linished conductor may be still further increased by heating itnntil soldering takes place, as also its strength may be increased by heating the compressed body to incipient or complete fusion simultaneously with or subsequently to the compression.

1t may be mentioned that electric conductors have already been manufactured both, of compressed metallic powder and of carbon and metal powders mixed; butsuch conductors, as regards sparking and Wear ontile commutator, are equivalent to metallic brushes, and the cohesion inl these bodies compressed of ordinary metal and carbon grains is less strong than the cohesion in ductors manufactured according to the pren ent invention.

Having now particularly dcsoribe'ii certaincd the nature of mysaid ation and in what manner the same is to be performed, I declare that what I claim ism l. An improved manufacture oi electric .EGO

Condncars., wherein grains of' eafzbo' are coated with memlic envelops and are subs@n quenty Subjted to compression, with or without. Bh@ application of heat, so as bocuse rfb@ grains to adheretogether mechanicallyA und form a compact; mass.

2. Electric conductors consisting of a compressed Ins-fsa of grains of carbon coated with i evenly mrbmed metallic snvelop, Substan'ay dascrhssd.,

In witness whereof I have hereunto set band in {wehen-se of two Witpessss.

VlVU-TGR LOWENLL. 

